NEW YORK (Reuters Health) - Athletes and hopeful job
applicants often hinge their careers on a clean drug test, but
the use of certain antibiotics may cause an unsuspecting
person to test positive for heroin even though they've never
touched the drug, according to study findings released
Tuesday.

Researchers led by Dr. Lindsey R. Baden of Harvard Medical
School in Boston, Massachusetts, investigated this problem
after they came across a patient in their practice who tested
positive for opiates, and who was also taking an antibiotic
called levofloxacin. The patient was nearly kicked out from a
drug treatment center because of the result, which later
proved to be false.

Opiates are a class of drugs that include the illegal drug
heroin, and several other controlled drugs such as methadone,
morphine, Demerol and codeine.
In their study, Baden and colleagues tested 13 different types
of antibiotics, including levofloxacin and Cipro, all
belonging to a class of chemicals called quinolones, to see
what effect they would have on commercial opiate tests.

The researchers diluted the antibiotics to concentrations that
would be expected to occur in urine and then tested the
antibiotic samples using five different commercial tests to
see if they would cause a positive result for opiates.
Two antibiotics, levofloxacin and ofloxacin, caused a strong
positive result on four of the five tests.

Most of the other antibiotics also caused a positive result on
at least two or three of the five tests. For example, Cipro,
the drug given to thousands of people to fight possible
anthrax exposure, resulted in a positive test in one out of
the five tests.
To confirm these results in people, they had six people take a
standard dose of one of the two antibiotics and collected
their urine samples every 6 hours for the next 48 hours.
On one of the five tests, all three patients taking
levofloxacin tested falsely positive within 2 hours and up to
22 hours after taking the drug. The results were similar in
patients taking ofloxacin, the investigators report in the
December 26th issue of The Journal of the American Medical
Association.

Baden told Reuters Health that he suspects that the false
positives result from the similar three-dimensional structures
of opiates and the antibiotics. He also pointed out that other
types of chemicals could cause a similar reaction.

According to Baden, it is possible that people have suffered
consequences of a false positive test, because ``a positive
drug test is often assumed true, while the protestations of
the person being tested are looked at as self-serving.''
Baden recommends that anyone who tests falsely positive for
opiates ask to have drug testing performed to confirm the
result.

SOURCE: The
Journal of the American Medical Association 2001;286:3115-